1. Field of the Invention
This invention relates to the processing of digital signals in such a way that there is a high probability of detecting and correcting errors in certain stages of the processing. In particular, the invention relates to deriving primary pulse code modulation (PCM) multi-bit digital signals from an analog signal, deriving secondary PCM signals from the same values of the analog signal as were included into the primary PCM signals, delaying either the primary or secondary signals, and combining groups of the delayed signals in interleaved sequence with groups of the relatively undelayed signals.
2. The Prior Art
It has been proposed in companion patent applications, Ser. No. 776,746 and 771,350, filed Feb. 8, 1977 and Feb. 23, 1977, respectively, both assigned to the assignee of the present application, to process analog audio signals on a video tape recorder (VTR). These companion applications, along with a third companion application, Ser. No. 860,883 filed Dec. 15, 1977, describe techniques for encoding the audio signals by means of PCM techniques and arranging the resultant pulse signals to correspond to a video format so as to be handled easily by a VTR.
The analog signals are sampled at a frequency at least substantially twice as high as the highest information frequency embodied in such signals. A convenient sampling rate is three times the horizontal line frequency rate of the video signal, because this makes the resultant sampled signal commensurate with video horizontal synchronizing signals incorporated into the psuedo-video format.
VTRs are capable of handling audio signals with excellent fidelity, but there is still an occasional problem of loss of signal due to a drop out or to a noise burst. Since the quality of reproduction possible with equipment of the type described hereinafter is sufficiently high to be consistent with commercial standards, it is important to avoid even occasional errors in the processed signals.